Can filamentous fungi form biofilms?
In the past few decades our fundamental understanding of how microorganisms grow and survive in natural settings or in host tissues has changed considerably. It is now widely accepted that microbes in nature rarely survive as solitary cells, but rather grow as biofilms. In fact, the formation of biofilms is so prevalent that it is likely to be a positively selected trait that became fixed very early in microbial evolution as an important feature for survival on surfaces in diverse or changing environments.
A biofilm can be described as a microbially derived sessile community characterized by cells that are irreversibly attached to a substratum or interface or to each other, are embedded in a matrix of extracellular polymeric substances that they have produced, and exhibit an altered phenotype with respect to growth rate and gene transcription. It is important to note that not all researchers apply the term biofilm synonymously. For example, another widely accepted biofilm definition describes a “microscopic mushroom-shaped” 3D community of microbial cells held in association and firmly attached to surfaces via an extracellular polymeric matrix that is permeated by water channels allowing efficient biomass exchange between the population and the environment. This definition encompasses many examples of biofilm structures in aqueous environments, but does not include surface-associated microbial growth in environments that are not saturated in water or fluid. The range of physical or environmental conditions necessary for the formation of biofilm structures is a debated topic. For example, surface-associated microbial growth in low water environments, such as on rocks, rhizospheres or the surfaces of buildings, have been termed unsaturated, terrestrial or subaerial biofilms by some authors. As a result of these diverse definitions, differences exist in the application of the terminology to various microbial assemblages, and it is unclear whether all assemblages qualify as biofilms versus aggregates, microbial mats, flocs or microcolonies.
In a broad context, biofilm formation involves genetically programmed changes in the organization and metabolism of the solitary or planktonic forms of microorganisms. Structurally, cells leave a motile, solitary or planktonic condition and become securely attached to a surface and/or other cells within an exopolymeric matrix. The structure of individual cells is not significantly altered, but the individuals become organized into a communal structure, encased in slime, and display novel characteristics and phenotypes. One frequently measurable change in the phenotype of cells in a biofilm, as compared to their planktonic counterparts, is significantly increased tolerance to chemical, biological or physical stresses. In fact, one of the most striking and consistently reported features of microbial populations growing as biofilms is their increased intrinsic resistance to antimicrobial agents. As a result, conventional antibiotic agents and biocides often fail to eradicate infectious microorganisms from hosts or from inert hard surfaces when present in a biofilm.
It is generally assumed that filamentous fungi, some of which have a significant impact on our health or our economy, do not form biofilms. In contrast to this assumption, this paper discusses recent findings supporting the hypothesis that surface-associated filamentous fungi can form biofilms. Based on these findings and on previous models for bacterial and yeast systems, it proposes preliminary criteria and a model for biofilm formation by filamentous fungi.
Can filamentous fungi form biofilms? Trends Microbiol. Oct 13 2009
Related:
- Candida parapsilosis secreted lipase is a major virulence factor
- Bugs Against Biofilms
- Who you gonna call? Slimebusters!
Tags: Biofilms, Biology, Environment, Medicine, Microbiology, Science
